Structural Change of Single-Crystalline Graphite under Plasma Irradiation

Under bombardment of hydrogen plasmas whose thermal energies are higher than the binding energy of target material, the structure of the surface of single-crystalline graphite dynamically turns into hydrogenated amorphous carbon via the chemical and physical reactions of incident hydrogen atoms. This structural change affects the processes of retention, reflection, and sputtering, which is an interesting issue of plasma-surface-interaction. Therefore, to investigate the retention of incident hydrogen atoms and the structural change of the graphite under plasma irradiation, hydrogen injection into a single-crystalline graphite is performed by binary-collision-approximation-based (BCA) simulation and the hybrid simulation of BCA and molecular dynamics simulation. As a result, it is found that the channeling effect, which is an effect peculiar to the crystalline structure, gradually disappears because the target material becomes amorphous. In addition, the time evolution of the bonding states of the target material under plasma irradiation is also investigated. (C) 2013 The Japan Society of Applied Physics